The present invention relates to hydraulic jacks and more particularly to cushioning devices for cushioning the end of stroke movement of the hydraulic jacks.
Many multi-stage hydraulic jacks are permitted to retract under freefall conditons due to gravity loads on the jacks. Occassionally, the end of the inner rod impacts against the head of the cylinder at the end of the stroke with sufficient force to cause structural damage to the jack. Although many snubbing or cushioning devices have been proposed for cushioning the end of the stroke movement, they all use the concept of restricting the flow of fluid from the actuating chamber through the inlet-outlet port. However, such cushioning devices are not readily adaptable to multi-stage hydraulic jacks since the elements making contact at the end of the stroke are generally disposed at the end of the hydraulic jack opposite to the end containing the inlet-outlet port.